Method and device for transmitting heating or cooling medium to a food product on a moving substrate

ABSTRACT

A device for transmitting a heating or cooling medium to a moving substrate which includes at least one continuous channel traversing at least a major portion of the width of the moving substrate for converting a multidirectional flow of the heating or cooling medium into a unidirectional flow, a device for removing and/or preventing the presence of foreign matter within the channel, and ovens and freezers employing the same.

TECHNICAL FIELD

The present invention is generally directed to a device for transmittinga heating or cooling medium to a moving substrate and particularly to adevice for transmitting a cool vapor such as air within an impingementfreezer for freezing food in which frost buildup is substantiallyeliminated.

BACKGROUND OF THE PRIOR ART

Commercial ovens and freezers typically rely on the transmission of aheating or cooling medium such as air to the food product by a large fanor blower. The fan or blower is situated proximate to a conveyor whichcarries the food through the heater or freezer for a time sufficient toheat or freeze the food product.

The food product entering the oven or freezer has a boundary layercomposed primarily of stagnant air which insulates the food product fromthe surrounding atmosphere. In order to effect proper cooking orfreezing, the boundary layer must be substantially reduced to expose thefood product directly to the heating or cooling medium.

Conventional fans or blowers generate a multidirectional flow of theheating or cooling vapor. Much of the vapor is scattered about thefreezer and only a portion of this scattered vapor reaches the foodproduct. At least a significant portion of the blown vapor, therefore,does not directly impinge on the food product in a perpendiculardirection. Under these conditions, the vapor which does contact the foodproduct often does not possess sufficient energy to substantially reducethe boundary layer. This results in inefficient heating or freezing orrequires excessively long exposures of the food product to the heatingor freezing operation.

Efforts have been made to reduce the amount of heating or cooling vaporwhich is scattered about the freezer. This has been accomplished byemploying a device within the oven or freezer which transforms themultidirectional air flow from the blower or fan into a unidirectionalflow of air directly toward the food product which has sufficient energyto reduce the boundary layer.

For example, Donald P. Smith, U.S. Pat. Nos. 3,884,213, 4,289,792 and4,338,911, disclose a cooking apparatus utilizing a series of spacedapart discrete jets of unidirectionally flowing air produced byappropriately spaced tubes.

Donald P. Smith, U.S. Pat. No. 4,479,776, discloses a heating/coolingapparatus having a thermal treatment zone for supplying columnated jetsof a gas to the exterior surface of a food product moving relativethereto in combination with at least one equilibration zone forpromoting heat transfer into or out of the interior portions of the foodproduct. A number of vertical spaced apart tubes are positioned in theheating/cooling section to direct a unidirectional air flow toward thefood product.

Mitchell C. Henke, U.S. Pat. No. 4,626,661, discloses the use of aplurality of nozzles spaced apart over the pathway of the food productfor delivering discrete jets of unidirectional heating/cooling air. Aplurality of high velocity air jets are also employed in Steven M. Shei,U.S. Pat. No. 4,757,800, in which impingement apertures direct heatedair in a unidirectional manner to heat the food product passing on aconveyor.

Another approach to providing unidirectional flow of air in an oven isdisclosed in Virgil L. Archer, U.S. Pat. No. 4,873,107. Instead ofemploying tubes for directing the heated air toward the food product asdiscussed above, there is provided a spaced array of rectangular slots.The multidirectional air from the fan or blower is caused to enter theslots and thereby attain a more orderly and direct flow toward the foodproduct. A similar arrangement of rectangular slots is disclosed inClement J. Luebke et al., U.S. Pat. No. 4,972,824.

Each of these heating/cooling devices provides an improvement over theuse of fans and blowers alone because they generally produce aunidirectional flow of heating/cooling air having sufficient energy toreduce the boundary layer of the food product. However, such devicesobtain these improvements by expending excessive energy to distributethe heating/cooling air to the food product. In addition, with respectto freezers, the tubes or slots used to form the unidirectional flowoften become plugged with frost. The buildup of frost tends to degradethe freezing operation over a period of time. Frost reduces the amountof heat transferred from the food product and, therefore, as the time ofthe freezing operation increases, the efficiency of the transfer of heatfrom the food product to the atmosphere decreases. In order to removethe frost to keep the air passageway open, it has been necessary to shutdown the freezer to melt the accumulated frost, resulting in delays andadditional cost of the process.

Accordingly, it would be desirable to employ a device for transmitting aheating or cooling medium such as air to a substrate such as a foodproduct on a conveyor belt in a more energy efficient manner byproviding for better distribution of the heating/cooling medium acrossthe width of the conveyor belt. It would also be of benefit to providebetter distribution of the heating/cooling medium from the source (e.g.the fan or the blower) to the food product.

Furthermore, with respect to the freezing of food, it would be ofsignificant benefit to prevent the buildup of frost in the freezerwithout having to terminate the freezing operation.

SUMMARY OF THE INVENTION

The present invention in its broadest aspects is generally directed to adevice for transmitting a heating or cooling medium to a movingsubstrate such as a food product on a conveyor belt. The devicecomprises at least one continuous channel traversing at least a majorportion of the width of the substrate for transforming amultidirectional flow of the heating or cooling medium into aunidirectional flow.

The continuous channel has a first opening for receiving the heating orcooling medium and a second opening for discharging the medium inproximity to the substrate. As the medium passes through the channelfrom the first to the second opening it is transformed into aunidirectional flow having sufficient energy to at least reduce theboundary layer of the food product. In addition, the continuous channelenables a greater rate of heat transfer from the food product thanconventional systems employing intermittent (non-continuous) slots ortubes. In a preferred form of the invention, the first opening of thechannel has a greater cross-sectional area than the second opening. Thelarger entrance area enables a greater volume of the medium to enter thechannel and facilitates the transformation of the medium into aunidirectional flow.

In accordance with one aspect of the invention particularly related tothe transmission of a cooling medium, means are provided forcontinuously cleaning the channel without having to terminate thefreezing operation. The cleaning means is insertable into the channeland movable along at least a portion of the length thereof. The cleaningmeans comprises at least one projection, preferably in the form of acleaning rod, extending into and along the height of each of thechannels from the first to the second opening. The projections aremovable within the channels along the length thereof and are adapted toloosely contact the walls of the channels as they move to remove and/orprevent the buildup of foreign matter including frost. The movement ofthe projections can be controlled in a manner which keeps the channelsfree of foreign matter while not interfering with the flow of thecooling medium through the channels.

In a further embodiment of the invention, the cleaning rods can beprovided with a pathway to allow a fluid to pass into the channel toassist in removing and/or preventing the buildup of frost and otherforeign matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of embodiments of the inventionand are not intended to limit the invention as encompassed by the claimsforming part of the application.

FIG. 1 is a partial side view of a conventional conveyor belt typefreezer;

FIG. 2 is a partial perspective view of one embodiment of the deviceused to form a unidirectional flow of the cooling medium in accordancewith the present invention;

FIG. 3 is an end view of an embodiment of a cleaning assembly inaccordance with the invention showing cleaning rods attached to amovable support mechanism;

FIG. 4A is a partial perspective view showing the placement of oneembodiment of the cleaning rods within channels of the unidirectionalflow device shown in FIG. 2 to effect cleaning thereof;

FIG. 4B is a partial perspective view similar to FIG. 4A showing hollowcleaning rods having openings for transmitting a fluid therethrough;

FIG. 5A is a top view of a support mechanism for supporting the cleaningrods and a conveyor mechanism for guiding one row of the cleaning rodsalong the length of the corresponding channels;

FIG. 5B is a top view similar to FIG. 5A showing a support mechanism andconveyor mechanism for guiding three rows of cleaning rods along thelength of the corresponding channels;

FIG. 6 is an end view of the support mechanism shown in FIG. 5B;

FIG. 7 is another embodiment of the unidirectional flow device whereinthe opening for receiving the cooling medium into the channels is ofgreater cross-sectional area than the opening for discharging thecooling medium from the channels onto the food product;

FIG. 8 is a perspective view of an impingement type freezer having threefreezer sections each employing both the unidirectional flow device andthe cleaning device of the present invention; and

FIG. 9 is a top view of one freezer section of the type shown in FIG. 8showing the cleaning rods positioned in the channels.

DETAILED DESCRIPTION OF THE INVENTION

The present invention shall be described with respect to a freezer forcontinuously freezing a food product by contacting the food product witha unidirectional flow of a cooling medium such as cold air, nitrogen orcarbon dioxide vapor. It should be understood that the invention is alsoapplicable to an oven for continuously heating a food product with aheating medium such as heated air.

Referring to FIG. 1, there is shown a conventional belt-type commercialfreezer customarily employed for freezing food products such as shrimp,chicken, chicken parts, scallops, vegetables, hamburger patties and thelike. The freezer 2 includes a housing 4 having an entry port 6 forreceiving the food product via a conveyor belt 8 driven by a motor 9.The entry port 6 leads to a freezer section 10 which is in the form of atunnel 12 where the food product 14 is frozen prior to leaving thefreezer 2 via an exit port 15 at the opposite end of the freezer.

A cooling medium is provided to the freezer section 10 in sufficientquantities so that the food product is frozen during passage through thetunnel 12. The cooling medium, such as air cooled by the presence of aliquid cryogen, is generated by a cooling section 16 comprised of asource of coolant 18, an exchange zone 20, and a fan or blower 22.

The source of coolant 18, for example a liquid cryogen (e.g. liquidnitrogen or carbon dioxide) is placed in proximity to the warmed vaporwhich has given its cooling duty to the food product in the exchangezone 20. The temperature of the warmed vapor is thereby reduced to wellbelow 32° F. (0° C.). The liquid cryogen is preferably sprayed into theexchange zone 20 through a nozzle or header (not shown) and thereby isbrought into contact with the moving food product 14 by the downdraftgenerated by the fan or blower 22. Specifically, the cooling medium isblown by the fan 22 in the general direction of the food product 14 asshown in FIG. 1 in the direction of the arrows. Upon eventual contactwith the food product 14, the cooling medium gives off its cooling dutyand is then drawn up into and reinserted into the exchange zone 20 bythe fan 22 where it is again cooled by contact with the source ofcoolant 18.

The type of freezer shown in FIG. 1 is disadvantageous because the flowof the cooling medium is multidirectional. While the cooling medium isblown away from the fan 22 in the general direction of the food product,a significant portion of the cooling medium will scatter about thefreezer section 10 before contacting the food product. As a result, theflow of the cooling medium loses some of its energy and, therefore, isnot efficient in reducing the boundary layer associated with theunfrozen food product. To compensate for this inefficient flow of thecooling medium, it is often necessary to increase the horsepower of thefan or blower which adds significantly to the cost of the process.

The present invention provides for a unidirectional flow of the coolingmedium so as to more efficiently reduce the boundary layer. In addition,a cleaning device is provided which prevents the buildup of frosttypically associated with prior freezers using conventional tubes andslots to form a unidirectional flow of the cooling medium.

Referring to FIG. 2, the present invention includes a device 30 forgenerating a unidirectional flow of a cooling medium toward a conveyorbelt having thereon a food product. The device 30 includes a pluralityof parallel, spaced apart inverted U-shaped troughs 32. Each trough 32has a wall 34 which lies proximate to, but spaced apart from, acorresponding wall 34 of an adjacent trough 32. The space between thewalls 34 of adjacent troughs 32 defines a continuous, preferablyparallelpiped shaped, channel 36 preferably having a first opening 38for receiving a multi-directional flow of the cooling medium and asecond opening 40 for discharging a unidirectional flow of the coolingmedium to the food product.

The unidirectional flow device 30 can be made of a variety of materialsincluding metals such as stainless steel, aluminum and the like, as wellas plastics such as polyethylene and polypropylene and the like. Thedimensions of the channel 36 are sufficient to establish a straight orunidirectional flow of the cooling medium as it leaves the secondopening 40. For this purpose, the height of the channel 36 is generallygreater than twice its width. For a typical size commercial freezer, theheight of the channel 36 will be in the range of from about 1 inch (2.54cm) to 12 inches (30.48 cm) and the diameter or cross-sectional lengthof the channel 36 is typically from about 0.25 inch to 1.00 inch. Thelength of the channel 36 measured from the front 42 to the rear 44 ofthe trough 32 is selected to run substantially the full width of theconveyor belt 8, typically about 36 inches (91.44 cm) for a commercialfreezer.

The second opening 40 is positioned at a distance from the food producttypically in the range of from about 1 to 4 inches (2.54 to 10.16 cm).The distance is chosen so as to insure that the unidirectional flow ofthe cooling medium is of sufficient velocity to reduce the boundarylayer of the food product, but does not move the food product as itpasses on the conveyer belt 8.

During continuous operation of the freezer some moisture from theatmosphere and the food product itself will enter the freezer sectioncausing the buildup of condensation in the form of frost on thecomponents of the freezer. In prior art devices, frost builds up on theinterior surfaces of the tubes or slots used to produce unidirectionalflow. If allowed to continue, the frost buildup will eventually retardand even prevent the flow of the cooling medium to the food product. Thebuildup of frost affects the rate of freezing by reducing the amount ofheat which can be removed from the food product because less of thecooling medium is able to reach the food product.

In accordance with one aspect of the present invention, there isprovided a cleaning device which is adapted to continually removeforeign matter, including frost, from the channels which are employedfor generating unidirectional flow. Referring to FIGS. 3, 4A and 4B, thecleaning device 50 includes a support member, shown as a bar 52 attachedat its opposed ends to a conveyor system 54 which is adapted to move thebar 52 along the length of the channels 36 as shown in FIG. 3 and asexplained in detail hereinafter.

Attached to the support bar 52 are a number of cleaning rods 56,preferably equally spaced apart, which are adapted to extend into eachof the similarly positioned channels 36 along the substantial heightthereof. The rods 56 are attached at one end to the bar 52 by a clamp 58or other suitable attachment mechanism such as a collar (see FIG. 4A)and the like.

The length of the rod is sufficient so that it extends substantially thefull height of the channel 36 as shown best in FIG. 4B. The width of therod is sufficient to enable the rod 56 to contact the walls 34 of thechannel 36 as the rod is moved along the length of the channel 36 by theconveyor 54 so as to remove frost or other foreign matter containedtherein. Accordingly, the width or diameter of the rods is slightly lessthan the width or diameter of the channels 36 [i.e. in the range ofabout 0.25 to 1.00 inch (0.63 to 2.54 cm)].

In another embodiment of the invention, the rods 56 may be provided witha passageway for transmitting a fluid such as air from a source into thechannels 36 to assist in preventing and/or removing frost and otherforeign matter. Referring to FIG. 4B, the rods 56 are provided with apassageway 60 leading to a plurality of spaced apart openings 62extending along the length of the rod 56. The fluid is fed into thepassageway 60 of the rod 56 from a corresponding passageway 64 of thesupporting bar 52 or in any other suitable manner. The pressure of thefluid supplied to the rod 56 should generate a flow of fluid out of theopenings 62 sufficient to prevent and/or remove foreign matter whichadheres to the interior of the walls 34 of the channel 36.

The cleaning device 50 is adapted to clean the entire volume of theparallelpiped shaped channels 36. Accordingly, the rods 56 must be movedalong substantially the entire length of the channel 36 which traversesthe width of the conveyor belt 8. In one embodiment of the invention, asbest shown in FIG. 3, a single bar 52 is provided for moving a singlerow of rods 56 along the entire length of the channel 36. As shown inFIG. 3, it is often desirable to cool the food product from above andbelow the conveyor belt 8 as shown by the arrows indicating the movementof the food product. Therefore, it is preferred to provideunidirectional flow devices 30 and corresponding cleaning devices 50both above and below the conveyor belt 8, with each single row of rodsmoving the entire length of the channel 36.

Movement of the cleaning rods 56 along the length of the channels 36 isaccomplished by a guidance system 66 for guiding the rods in a preciselinear path and a system 68, either a pneumatic system or a hydraulicsystem, but preferably a pneumatic system, for supplying the forcenecessary to move the rods 56. Hereinafter, all reference to the system68 shall be limited to a pneumatic system. It shall be understood,however, that the force necessary to move the rods 56 can be supplied bya hydraulic system as well. Together the guidance system 66 and thepneumatic system 68 comprise the conveyor system 54.

In the embodiment shown in FIG. 5A, the single support bar 52 must bemoved along the entire length of the channels 36. Accordingly, thepneumatic system 68 must be of sufficient size to provide theappropriate movement for the support bar 52. Smaller pneumatic systemsmay be used by modifying the cleaning device to include more than onerow of cleaning rods, with each row moving only a fraction of the lengthof the channels. In this way, the size and cost of the pneumatic system68 can be minimized.

Referring to FIGS. 5B and 6, there is shown an embodiment of thecleaning device in accordance with the present invention employing threerows of cleaning rods 36a-36c.

Referring to FIG. 5A, the guidance system 66 comprises a guide rod 70positioned within the freezer section 10 by guide blocks 72 having anopening 74 allowing movement of the rod 70 therethrough. The guidancesystem 66 also includes a device 76 for attaching the guide rod 70 tothe support bar 52. The device 76 includes a beam 78 which runs parallelto the guide rod 70 and is attached to the support bar 52 by a clampingdevice 80. The ends of the beam 78 extend at a right angle toward theguide rod 70 and are attached thereto by clamps 82a and 82b.

Movement of the support bar 52 is accomplished by the pneumatic system68 which includes a pneumatic cylinder. The pneumatic cylinder 84 housestherein a piston 86 which is shorter than the cylinder and, therefore,the piston is movable within the cylinder. The cylinder has opposedopenings 88 and 90 for receiving and discharging air (or other gas)which is used to move the piston within the cylinder. The cylinder isattached at one end to the housing 4 of the freezer 2 by a bracket 92and an extension 94 attached to the piston 86, and at the opposed end tothe support bar 52 by a bracket 96 and a corresponding extension 98 ofthe piston 86. The pneumatic system 68 operates by pumping airalternatively into the openings 88 and 90 to move the piston 86 forwardand backward, respectively, within the cylinder 84 and, therefore, movethe support bar 52 in the same direction. More specifically, when air ispumped into the opening 90, it exerts a force on the piston 86 movingthe piston forward. The piston 86 exerts pressure against the supportbar 52 thereby moving the bar 52 in the same direction.

As previously indicated, the support bar 52 is attached to the guidancesystem 66 via the beam 78 and clamps 80a and 80b. Accordingly, as thepiston 86 moves forward, the guidance system 66 including the guide bar70 moves in the same direction as the piston 86. A precise linear pathis maintained because the guide bar 70 is aligned during movement by theguide blocks 72.

The guidance system 66 is moved in the opposite direction by reversingthe flow of the air. If air is pumped into the opening 88, the piston 86will move backwards causing like movement of the guidance system 66 aswell as the support bar 52.

Referring to FIG. 5B, three rows of cleaning rods 36a-36c are supportedby three corresponding bars 52a-52c through collars 58. One end of thepneumatic system 68 is attached to the middle bar 52b. The bars 52a-52care moved by the guidance system 66 and the pneumatic system 68 in thesame manner as described in connection with the embodiment of FIG. 5A.However, each bar 52a-52c moves only about one-third the length of thechannels 36, thereby reducing the size of the pneumatic system 68.

Accordingly, the cleaning device 50 can be constructed so that each rowof cleaning rods moves a designated fraction of the length of thechannels 36. Employing multiple rows of cleaning rods in this mannerallows use of a smaller pneumatic system which is less costly than asingle pneumatic system which must move the entire width of the conveyorbelt.

The unidirectional flow device 30 can be modified to provide an evenmore effective transition from multidirectional to unidirectional flow.Referring to FIG. 7, there is shown a unidirectional flow device 100 inaccordance with a preferred aspect of the invention in which theentrance to the channels is expanded to accommodate a greater volume ofthe cooling medium and to better facilitate the transition frommultidirectional to unidirectional flow. The device 100 has adjacentwalls 102 forming a channel 104, preferably in the shape of aparallelpiped. The first opening 106, unlike the unidirectional flowdevice shown in the embodiment of FIG. 2, is formed by a pair ofdiverging walls 108a and 108b so that the cross-sectional area of thefirst opening 106 is greater than the second opening 110 which leads tothe food product.

Expanding the cross-sectional dimension of the first opening 106facilitates the manner in which the cooling medium is funneled into thechannel 104. The larger opening permits a greater quantity of coolingmedium to enter the channel 104 and, therefore, generates a moreefficient stream of the cooling medium out of the second opening 110. Inaddition, the pressure drop through the channels 104 is reduced therebyreducing the horsepower needed to drive the cooling medium through thechannels 104.

Expanding the cross-sectional area of the opening 106 also reduces thelikelihood of moisture buildup within the channel 104. This is becausemoisture buildup on the diverging wall 108a and 108b will not obstructthe flow of the cooling medium through the channel 104.

In another embodiment of the invention as shown in FIG. 8, multipleunidirectional flow devices and corresponding cleaning devices may behoused in a single freezer. As shown specifically in FIG. 8, three pairsof such devices are positioned within a single freezer section 10. Eachpair of devices occupies approximately 1/3 of the length of the freezersection 10 and functions as described previously in connection with theembodiments of FIGS. 2-7.

The operation of the present invention can be best explained byreference to FIGS. 2, 3, 7-0. FIG. 9 shows an embodiment of theinvention with one unidirectional flow device and cleaning devicecontained within the freezer section. Unfrozen food product 14 entersthe freezer 2 on a conveyor belt 8 through the opening 6 where it istransported to the freezer section 10 through the tunnel 12. Positionedabove and/or below (see FIGS. 8 and 9) the conveyor belt 8 is at leastone unidirectional flow device 30, preferably operatively associatedwith a cleaning device 50 of the present invention. The freezer section10 receives a multidirectional flow of the cooling medium from theexchange zone 20 via the fan 22 as shown best in FIG. 9 which enters thefirst opening 38 of the flow device as shown best in FIG. 8. The coolingmedium which enters the channel 36 is transformed into a unidirectionalflow as it passes through the channel 36 and out the second opening 40(see FIGS. 2 and 7).

Upon leaving the second opening 40, the cooling medium comes intoimmediate contact with the food product and gives off its cooling dutywhile being deflected into the trough 32 where it is drawn back to theexchange zone 20 and is provided with additional coolant to lower thetemperature thereof.

During operation of the freezer 2, moisture can enter the freezer from anumber of locations, principally through the opening 6 for receiving theunfrozen food product and from the food product 14 itself. The moisturecondenses on various components of the freezer causing the buildup offrost. The channels 36 of unidirectional flow device 30 are particularlysusceptible to the buildup of frost and must therefore be cleaned.

Prevention of frost buildup is accomplished by the cleaning device 50.As the food product 14 moves on the conveyor 8, the cleaning rods 56 areguided along the length of the channels 36 by the guidance system 66through the power provided by the pneumatic system 68.

In the embodiment shown best in FIG. 8, each channel 36 is cleaned bythree cleaning rods, each adapted to travel about one-third of the totallength of the channel. This configuration reduces the size of thepneumatic requirements and, therefore, lowers the cost of the freezingoperation. The rods 56 are supported on three supporting bars 52a-52c,respectively. The bars move in unison with each other and thereby cleanthe entire channel while each rod travels only one-third the length ofeach channel.

The speed of the bars, and therefore of the rods, is sufficient toprevent the buildup of frost while not interfering with the flow of thecooling medium through the channel. Preferably, the bars move at therate of about 0.5 to 10 ft/min. Movement of the bars need not becontinuous. For example, the bars may be moved intermittently duringtheir travel along the length of the channel or may be discontinued fora period of time. The selection of a suitable mode of operation andtravel speed will be dependant on the rate of frost buildup in thefreezer.

EXAMPLE

A standard belt-type freezer of the type shown in FIG. 1 was employed togenerate data for determining the amount of time needed to freeze ahamburger patty measuring 4.5 inches (11.43 cm) in diameter, 0.5 inch(1.27 cm) thick and weighing 4 ounces (113 grams). The heat transfercoefficient for this type of freezer was determined to be 7 BTUs/lb-ft²-° F. [40 W÷(m² -° C.)].

The food product enters the freezer at 30° F. (-1° C) and must exit thefreezer at 0° F. (-18° C). As a result 28 BTUs (29.5 Kjoules) of heatmust be removed from the hamburger patty. The freezer section isoperated at -80° F. (-62° C.) and it will take approximately 11.5minutes to freeze the hamburger patty to 0° F. (-18° C).

The impingement type freezer of the present invention was determined tohave a heat transfer coefficient of 17 BTUs/lb-ft² -° F. [96.5 W÷(m² -°C.0]. Operating under the same conditions as described for the standardbelt-type freezer, the same hamburger patty will freeze to 0° F. (-18°C.) in only 4.7 minutes.

What is claimed is:
 1. A device for transmitting a heating or coolingmedium to a food product on a moving substrate comprising:(a) at leastone continuous channel traversing at least a major portion of the widthof the moving substrate, said channel having a first opening forreceiving a multidirectional flow of the heating or cooling medium and asecond opening for discharging the heating or cooling medium in aunidirectional flow toward the moving substrate.
 2. The device of claim1 wherein the channel is in the shape of a parallelpiped.
 3. The deviceof claim 1 wherein the height of the channel is at least twice the widthof the channel.
 4. The device of claim 1 wherein the cross-sectionalarea of the first opening is greater than the cross-sectional area ofthe second opening.
 5. The device of claim 4 wherein the first openingis V-shaped.
 6. The device of claim 1 further comprising cleaning meansinsertable into said channel and movable along at least a portion of thelength of the channel for removing or preventing the presence of foreignmatter within the channel.
 7. The device of claim 6 wherein the cleaningmeans further comprises at least one support member extendingsubstantially perpendicular to the channel for supporting the cleaningmeans within the channel, and means for moving the at least one supportmember along the length of the channel.
 8. The device of claim 7comprising a plurality of spaced apart channels traversing a substantialportion of the moving substrate, said cleaning means comprising at leastone rod extending into and substantially the entire height of each ofthe channels and being adapted to contact the walls of the channelsduring movement of the cleaning means along the length of the channel.9. The device of claim 8 comprising a plurality of rows of said rods,each rod of each row extending into and along substantially the entireheight of the respective channel, each row of rods adapted to move alonga fraction of the length of the channel wherein the entire length ofeach channel is traversed by the combined movement of each row of rods.10. The device of claim 7 further comprising guide means for guiding thecleaning means in at least a substantially linear path along the lengthof the channels.
 11. The device of claim 10 wherein the guide meanscomprises, a guide beam extending parallel to the channels and a guideblock having an opening for permitting the guide beam to travel in saidlinear path, and means for securing the at least one support member tothe guide beam so that the support member moves in unison with the guidebeam.
 12. The device of claim 7 wherein the means for moving the atleast one support member comprises a pneumatic means attached at one endto one of the support members and adapted to urge the at least onesupport member forward or backward along the length of the channels. 13.The device of claim 8 wherein the at least one rod has a passagewaytherein for receiving a fluid and at least one opening for dischargingthe fluid into the channel.
 14. A device for heating or cooling a foodproduct comprising:(a) an entry port for receiving a food product; (b)conveyor means for transporting the food product from the entry port toan exit port. (c) means for generating a multidirectional flow of aheating or cooling medium; and (d) a food treatment section traversed bythe conveyor means and comprising at least one continuous channeltraversing at least a major portion of the width of the conveyor means,said channel having a first opening for receiving the multidirectionalflow of the heating or cooling medium and a second opening fordischarging the heating or cooling medium in a unidirectional flowtoward the conveyor means.
 15. The device of claim 14 wherein thechannel is in the shape of a parallelpiped.
 16. The device of claim 14wherein the height of the channel is at least twice the width of thechannel.
 17. The device of claim 14 wherein the cross-sectional area ofthe first opening is greater than the cross-sectional area of the secondopening.
 18. The device of claim 17 wherein the first opening isV-shaped.
 19. The device of claim 14 further comprising cleaning meansinsertable into said channel and movable along at least a portion of thelength of the channel for removing or preventing the presence of foreignmatter within the channel.
 20. The device of claim 19 wherein thecleaning means further comprises at least one support member extendingsubstantially perpendicular to the channel for supporting the cleaningmeans within the channel, and means for moving the at least one supportmember along the length of the channel.
 21. The device of claim 20comprising a plurality of spaced apart channels traversing a substantialportion of the conveyor means, said cleaning means comprising at leastone rod extending into and along substantially the entire height of eachof the channels and being adapted to contact the walls of the channelsduring movement of the cleaning means along the length of the channel.22. The device of claim 21 comprising a plurality of rows of said rods,each rod of each row extending into and along substantially the entireheight of the respective channel, each row of rods adapted to move alonga fraction of the length of the channel wherein the entire length ofeach channel is traversed by the combined movement of each row of rods.23. The device of claim 20 further comprising guide means for guidingthe cleaning means in at least a substantially linear path along thelength of the channels.
 24. The device of claim 23 wherein the guidemeans comprises, a guide beam extending parallel to the channels and aguide block having an opening for permitting the guide beam to travel insaid linear path, and means for securing the at least one support memberto the guide beam so that the at least one support member moves inunison with the guide beam.
 25. The device of claim 20 wherein the meansfor moving the at least one support member comprises a pneumatic meansattached at one end to one of the support members and adapted to urgethe at least one support member forward or backward along the length ofthe channels.
 26. The device of claim 21 wherein the at least one rodhas a pathway therein for receiving a fluid and at least one opening fordischarging the fluid into the channel.
 27. The device of claim 14 inwhich the food treatment section is a freezer and the continuous channeldischarges a cooling medium in a unidirectional flow toward the conveyormeans.
 28. A method of heating or cooling a food productcomprising:passing a multidirectional flow of a heating or coolingmedium into at least one continuous channel traversing at least a majorportion of the width of a moving substrate having thereon said foodproduct, and discharging the heating or cooling medium in aunidirectional flow through a second opening toward the food product onsaid moving substrate.
 29. The method of claim 28, further comprisinginserting at least one cleaning rod into said at least one continuouschannel and moving the cleaning rod over substantially the entire lengthof the at least one channel to remove or prevent the presence of foreignmatter.